There’s a famous joke in Washington that most Senators look in the mirror and see a future president.

That’s never really borne out in reality. The unwieldy cast of GOP presidential primary candidates in 2016 had 17 people running, only four of whom were sitting senators. Since 1960, only two senators, John F. Kennedy and Barack Obama, went straight to the White House from Capitol Hill.

But the 2020 Democratic presidential primary is already spilling over with members of Congress hoping to be the one to unseat Donald Trump. Not only are there expected to be an unheard of number of senators and representatives running, several are early front runners.

That’s a head-spinning list that means the next two years on Capitol Hill will serve as a staging ground for the presidential campaign. Every floor speech, every bill sponsored, every committee hearing statement by these members will be viewed through the lens of presidential politics.

While some of the candidates, like Sen. Casey and Rep. Ryan, will try to appeal to the moderate, white, working class voter that some Democrats believe cost them the election to Trump, most of the Democrats will be trying to prove their liberal bona fides to shore up a base that in 2016 showed a hunger for a candidate with bold and ambitious ideas.

The party is already shifting left, with a record number of newly-elected members joining the Congressional Progressives Caucus and pledging to push for big ticket items like universal health care and renewable energy.

A good example is “Medicare for all," the Bernie Sanders plan to model a single payer health care system after the popular entitlement program for seniors. It began as a pie-in-the-sky proposal and morphed into a litmus test issue for Democrats in the midterms. Many of the leading 2020 hopefuls are cosponsors of Sanders' bill, including Booker, Gillibrand, Harris and Warren.

James Thurber, founder and director of the Center for Congressional and Presidential Studies (CCPS) at American University, called the sheer number of members of Congress “unprecedented,” and said with so many personalities trying to stand out, it will be very difficult for the Democrats to unify on Capitol Hill over the next two years.

“It will be difficult to find a coalition around a particular position because each of the individuals will want to show prospective supporters that they are out there leading and have a position,” Thurber said. “They will try to distinguish from each other, show they are different than each other. That means a lot of show horses instead of work horses."

The Senate more than the House, which is bigger and has stricter rules for procedure, has always been a place where people can showboat. When it comes to running for president, the disadvantage of a full-time job in Washington means less time spent on retail politics in places like Iowa and New Hampshire. But the Senate provides a stage other candidates don’t have. And if other election years are a guide, once the campaign really start going, members of Congress tend to forgo their day job for time on the trail.

There are other downsides too, especially for those who have been around for a while. A long legislative history means more votes and positions for opponents to pick apart and parse. Votes, especially on multi-faceted pieces of legislation, are often nuanced and difficult to defend in a campaign ad or stump speech.

Most famously, in 2008, which saw eight senators initially run on the Democratic side, Barack Obama hammered frontrunner Hillary Clinton on her vote for the war in Iraq. Obama was not yet in Washington, and never had to cast that difficult vote.

The issue came back to haunt her in 2016 when Sanders, who voted against the war, brought it up in a debate.

The greatest impact of all these lawmakers eyeing the White House is there will also be no incentive to negotiate with its current occupant. It won’t be politically expedient to be seen ceding any ground to Trump and the Republicans.

And so, expect another two years in Washington of little progress and a lot more grandstanding.